ECON222 WEEK3 -Matrices-3(HW WEEK4)

ECON222 WEEK3 -Matrices-3(HW WEEK4) - Lecture 7 Topic...

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1 1 Lecture 7: Topic: Matrices Reading for this lecture H&P, Ch 6, Sect 6.3. Homework for Tutorial in Week 4 Ex 6.3, pp. 248-249, problems 7, 15, 23, 27, 63. 2 Conformability for Multiplication The product, AB , of two matrices, A and B , exists if, and only if, the number of columns in A equals the number of rows in B . In the following example AB exists and has 2 rows and 2 columns. 0 1 2 3 4 5 A = 6 7 8 9 10 11 B = 3 The Product of 2 Matrices The element in the i th row and j th column of AB is the sum of products of elements in the i th row of A and the j th column of B . 0 1 2 3 4 5 6 7 8 9 10 11 AB = 4 Conformability for Multiplication The product, BA , of two matrices, A and B , exists if, and only if, the number of columns in B equals the number of rows in A . In the following example, BA exists and has 3 rows and 3 columns. 0 1 2 3 4 5 A = 6 7 8 9 10 11 B = 5 The Product of 2 Matrices 0 1 2 3 4 5 6 7 8 9 10 11 BA = 6 Conformability for Multiplication If the number of columns in A does not equal the number of rows in B then the product, AB , of the two matrices does not exist.

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ECON222 WEEK3 -Matrices-3(HW WEEK4) - Lecture 7 Topic...

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